Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Partially purified selenoprotein P from rat plasma was digested with either trypsin, endoprotease Lys-C, or endoprotease Arg-C and analyzed by high pressure liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Several 75Se-labeled peptides were detected. The moles of selenium in selenoprotein P were estimated based on the 75Se content of the 75Se-labeled peptide fragments. Using this method, selenoprotein P was shown to contain approximately 9 moles of selenium. This is the first report of a selenoprotein containing more than one selenium per polypeptide. These findings support the proposed function of this protein in selenium transport.
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PMID:Multiple selenocysteine content of selenoprotein P in rats. 214 60

The catalytic activity of human tryptase, a mast cell neutral endoprotease, is expressed when the enzyme is in its tetrameric form, but is lost under physiologic conditions concomitant with a quaternary structural alteration involving conversion to a monomeric form. The associated changes in the CD spectra noted in the current study indicate accompanying alterations in the secondary structure of the protein. In particular, the progressive disappearance of the negative minimum centered at 228 nm suggests an effect on beta-sheet structure, which may be important for monomer-monomer interaction and/or stabilization of catalytic activity. Dextran sulfate, like heparin, stabilizes the catalytic activity and quaternary structure of tryptase and also maintains the native secondary structure of the enzyme at and beyond a temperature of 40 degrees C. Dextran sulfate-stabilized tryptase therefore was used as an immunogen to which were produced three murine mAb (B2, C11, and G4) recognizing the catalytically active form of the enzyme. Inactive tryptase bound to plastic microtiter wells was not recognized by any of the newly made antibodies, whereas inactive tryptase in solution was recognized by G4, which when biotinylated, could be used as a detector antibody in a sandwich ELISA for tryptase. Each of the newly made mAb recognized the catalytically active form of tryptase. Thus, alterations in epitopes, perhaps reflecting tertiary structural alterations as well as changes in secondary and quaternary conformations, occur with tryptase inactivation. A pragmatic result of these newly generated antibodies is the affinity purification to homogeneity of active tryptase by sequential chromatography with B2 coupled to CH-Sepharose and heparin-agarose. Tryptase purified by this technique had a specific activity with p-tosyl-L-arginine methyl ester of 117 +/- 9 U/mg and had 3.9 +/- 0.3 active sites per molecule of active enzyme (134,000 m.w.) as titrated with p-nitrophenyl-p'-guanidinobenzoate. The spectral and immunologic data in the current study are consistent with concerted conformational alterations in the secondary and tertiary as well as quaternary structures of tryptase associated with loss of catalytic activity. Failure to reverse any of these alterations with dextran sulfate suggests that the pathway of tetramer assembly in vivo is more complicated than simple subunit association.
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PMID:Immunologic and physicochemical evidence for conformational changes occurring on conversion of human mast cell tryptase from active tetramer to inactive monomer. Production of monoclonal antibodies recognizing active tryptase. 217 9

We have extracted, characterized, and partially purified an enzyme from secretory granules from rat small intestinal mucosa which cleaves a synthetic prosomatostatin substrate on the carboxyl side of a single arginine residue. This substrate Leu-Gln-Arg-Ser-Ala-Asn-Ser-NH2 contains the monobasic site at which mammalian prosomatostatin is cleaved in vivo to generate somatostatin-28. This activity was released from the granules by osmotic shock followed by extraction with 500 mM KCl. The enzyme had a molecular weight of about 55,000, a pH optimum of about 7.5, and a Km for the synthetic substrate of 20 microM. It was partially inhibited by diisopropyl fluorophosphate, phenylmethanesulfonyl fluoride, iodoacetate, soybean trypsin inhibitor, and EDTA. It was also very sensitive to aprotinin (complete inhibition at 25 micrograms/ml) but was not inhibited by bestatin, pepstatin, or p-chloromercuribenzoate. This endoprotease was unable to cleave three small trypsin and kallikrein substrates (N alpha-benzoyl-L-arginine ethyl ester, N alpha-benzoyl-DL-arginine p-nitroanilide, and N alpha-benzoyl-L-arginine 7-amido-4-methylcoumarin). It was unable to cleave either the Arg-Asp bond in CCK 12 or the Arg-Glu and Arg-Met bonds of synthetic peptides corresponding to sequences of anglerfish prosomatostatin II situated upstream from the somatostatin-28 domain. These observations together suggest that adjacent amino acids play a role in determining the conformational specificity of the monobasic cleavage. This soluble enzyme was also able to cleave three synthetic substrates containing dibasic residues (Arg-Lys or Lys-Arg) on the carboxyl side of the arginine, although it did so less rapidly than at the monobasic cleavage sites. When incubated with partially purified prosomatostatin from anglerfish pancreas, significant quantities of somatostatin-28 II were produced. All these cleavages were completely blocked by preincubation with aprotinin. Although further work is required to clarify the physiological role of this enzyme, it appears, in view of its catalytic properties, this endoprotease could be involved in the conversion of prosomatostatin to somatostatin-28 in intestine mucosal secretory cells.
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PMID:Characterization of an endoprotease from rat small intestinal mucosal secretory granules which generates somatostatin-28 from prosomatostatin by cleavage after a single arginine residue. 256 94

We have investigated the domain of the bindin polypeptide that selectively associates with gel-phase phospholipid vesicles. We found that small trypsin fragments of bindin retain the ability to selectively associate with gel-phase vesicles. The primary amino acid sequence of bindin suggests that these peptides are derived from the central portion of the polypeptide between residues 77 and 126, which is the most hydrophobic region of bindin. We have also employed 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine (TID) and novel, radioiodinated, photoactivatable derivatives of the polar head group of phosphatidylethanolamine (ASD-PE and ASA-PE) to identify membrane-associated polypeptide segments after the transfer of radiolabel from the probe to the bindin polypeptide. After photolysis, bindin was selectively labeled only from probes incorporated in gel-phase vesicles. The labeling of bindin was much more efficient from the head group probes ASA-PE and ASD-PE (8 and 2% of the total label, respectively) in comparison to the hydrophobic probe TID (less than 0.02% of the total label), suggesting that bindin is localized within the polar part of the bilayer. Protease mapping experiments with V8 protease, trypsin, and endoprotease Lys-C suggest that some of the probe label is distributed along the amino-terminal portion of bindin between residues 1 and 76 and the rest of the label is restricted to the segments between residues 77 and 126 which also selectively bind to gel-phase vesicles. The carboxyl-terminal portion of bindin between residues 127 and 236 is not labeled.
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PMID:Analysis of the membrane-interacting domain of the sea urchin sperm adhesive protein bindin. 260 49

The major apolipoproteins associated with oil-storage bodies have been isolated from the mature seeds of six different species of the family Cruciferae. The apolipoproteins were all of molecular mass 19-20 kDa. They were highly abundant in mature seed tissue, accounting for up to 20% total seed proteins, and were localized exclusively on the membranes of oil-storage bodies. Antibodies were raised in rabbits and mice against the six purified apolipoproteins. In each case, the antibodies specifically recognized 19-20 kDa polypeptides on immunoblots of total seed proteins from 15 different species of the Cruciferae. The extent of the immunological cross-reactivity among the six purified seed apolipoproteins of the Cruciferae was investigated quantitatively using enzyme-linked immunosorbent assay. Very high levels of cross-reactivity were obtained, in contrast to a complete lack of cross-reactivity observed when the major seed apolipoprotein of a non-crucifer, Glycine max, was assayed. Peptide mapping studies showed that the different crucifer seed apolipoproteins gave rise to similar proteolytic cleavage products following treatment with Staphylococcus aureus V8 protease, Lysobacter enzymogenes Lys-C endoprotease, and trypsin. The patterns of immunogenic proteolytic cleavage products of the different apolipoproteins were also similar. We propose that there is a family of abundant 19-20 kDa apolipoproteins in mature seeds of oil-bearing Cruciferae. These apolipoproteins are all major components of the membranes of oil-storage bodies. The apolipoproteins are therefore very closely related with respect to their structure, function, and immunological properties.
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PMID:An immunologically related family of apolipoproteins associated with triacylglycerol storage in the Cruciferae. 277 66

Protein L-isoaspartyl methyltransferase (PIMT) transfers the methyl group of S-adenosyl-L-methionine to free alpha-carboxyl groups of atypical L-isoaspartyl residues in proteins. The complete primary structure of the type I isoform of bovine brain PIMT was determined by sequence analysis of peptides generated by endoprotease Lys-C, trypsin, cyanogen bromide, and endoprotease Asp-N digests. The correct composition of every peptide was verified by fast atom bombardment mass spectrometry. The efficiency of sequencing by tandem mass spectrometry was examined for several peptides by comparing its speed and accuracy with automated Edman degradation. Tandem mass spectrometry was used to determine the structure of the NH2-terminal blocked peptide derived from a hydroxylamine cleavage. PIMT is 226 residues with Mr = 24,500 and contains acetyl alanine as the amino-terminal residue. The partial sequence (141 residues from 8 tryptic peptides) of a homologous human red cell PIMT (Gilbert, J. M., Fowler, A., Bleibaum, J., and Clarke, S. (1988) Biochemistry 27, 5227-5233) shows a 97% identity with the corresponding peptides of the bovine brain enzyme. The complete brain enzyme sequence reported here bears no significant homology to any other known class of methyltransferase including those which methylate the side chain gamma-carboxyl group of receptor proteins involved in bacterial chemotaxis.
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PMID:The primary structure of a protein carboxyl methyltransferase from bovine brain that selectively methylates L-isoaspartyl sites. 277 70

The selective processing activity which generates both the NH2- and COOH-terminal fragments of the octacosapeptide somatostatin-28 (S-28) was investigated. Separation into two distinct proteolytic activities was achieved by ion-exchange chromatography. An endoprotease cleaving either the substrate Pro-Arg-Glu-Arg-Lys-Ala-Gly-Ala-Lys-Asn-Tyr-NH2, i.e. [Ala17,Tyr20]S-28-(10-20)-NH2 (peptide I), or the octacosapeptide somatostatin-28, on the NH2 side of the Arg-Lys doublet was separated from an aminopeptidase B-like activity. Whereas the endoprotease cleaves a single peptide bond, between Glu12 and Arg13 of S-28, the aminopeptidase B-like enzyme removes both Arg13 and Lys14 stepwise from the NH2 terminus of the corresponding COOH-terminal fragment. This endoprotease activity peaks around pH 8.5, whereas the optimal aminopeptidase B-like activity is in the pH range 6.2-8.5. Combination of both enzymes resulted in the recovery of the overall S-28 convertase activity with an optimal pH at 7. In addition, this endoprotease appears to be very sensitive to divalent cations since it is strongly inhibited by chelating agents. The use of selectively modified undecapeptides derived from the reference substrate peptide I by a single modification of the amino acids Glu12, Arg13, and Lys14 at the cleavage locus showed that both basic residues are critically important, whereas Glu12 is not. It is proposed that S-28 processing involves a divalent cation-sensitive endoprotease that is sensitive to thiol reagents, which cleaves before the Arg-Lys doublet, which is not trypsin-like, and whose action is coupled to an aminopeptidase B-like enzyme.
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PMID:Enzymes that process somatostatin precursors. A novel endoprotease that cleaves before the arginine-lysine doublet is involved in somatostatin-28 convertase activity of rat brain cortex. 288 28

Two neuropeptide precursor processing enzyme systems were characterized in the rat brain cortex and bovine neurohypophysis and corpus luteum. The first one combines the action of a 90 kDa endoprotease which cleaves somatostatin-28 before the Arg-Lys doublet and that of an aminopeptidase B-like enzyme. The second system associates the action of a 58 kDa endoprotease cleaving pro-ocytocin/neurophysin (1-20) after the Lys-Arg dibasic moiety and a carboxypeptidase B-like activity. Both systems appear to be located in membrane-limited secretory vesicles of the producing organs, and to exhibit the properties of metallo-enzymes sensitive to divalent cation chelators. In contrast, they do not show the characteristics of serine-proteases and of trypsin-like enzymes. Studies with substrate analogs selectively modified at the basic doublet indicated that the integrity of both basic amino acids is essential but that conformational parameters, probably governed by the amino acid sequences flanking the basic doublet, play an important role. These data will be discussed in relation to a hypothesis on the predicted preferred secondary structure of these restriction loci.
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PMID:Somatostatin-28 and pro-ocytocin/neurophysin convertases: basic pair selective endoproteases involved in pro-hormone processing in the rat brain cortex and bovine corpus luteum. 290 27

The digestive tracts of adult and juvenile Dover sole were examined for protease activities. A pepsin-like protease with an optimal pH value of 1.7 predominated in the stomach region, but the main endoprotease action in the foregut, midgut and hindgut regions was optimal in the range of pH 9.5-10.5 and showed good activity towards elastin orcein. Experiments using synthetic substrates suggested the presence of chymotrypsin- and trypsin-like activities optimal between pH 7 and 8. Collagenase activity was also shown to exist in this pH region. The presence of enzymes corresponding to carboxypeptidases a and b and leucine aminopeptidase was indicated. The possible significance of these results to the farming of Dover sole is discussed.
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PMID:Metabolism in marine flatfish. II. Protein digestion in Dover sole (Solea solea L.). 299 Aug 7

The primary structure of angiogenin is 33% identical to that of bovine pancreatic ribonuclease (RNase), but the enzymatic activities of the two proteins differ markedly. Similarly, their susceptibilities to limited proteolysis differ as well. In contrast to RNase, angiogenin totally resists proteolysis by subtilisin. Indeed, among 16 proteases examined, only endoprotease Lys-C, trypsin, and pepsin are able to cleave angiogenin. Even with prolonged incubation, endoprotease Lys-C selectively cleaves the Lys-60-Asn-61 bond; the product retains full ribonucleolytic activity. Initially, trypsin also cleaves this same bond, but with time it causes extensive degradation. Pepsin, at pH 2, cleaves the Phe-9-Leu-10 bond, to give angiogenin (10-123), which displays approximately 15% of the native activity toward ribosomal RNA (rRNA). The susceptibility to proteolysis and/or the sites of cleavage of angiogenin and bovine RNase differ markedly despite their structural homology. These differences are considered in terms of the amino acid sequences of the two proteins.
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PMID:Conformational characterization of human angiogenin by limited proteolysis. 315 Dec 51


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